The apparatus described in U.S. Pat. No. 4,366,125, which is incorporated herein by reference in its entirety, including any references cited therein, generates a hydrogen peroxide mist by an ultrasonic wave vibrator. The mist adheres to the surface of materials being sterilized and is then irradiated with ultraviolet-ray lamps. U.S. Pat. Nos. 5,878,355 and 6,102,992, each of which is incorporated herein by reference in its entirety, including any references cited therein, disclose a method and device for decontamination of a contaminated process area whereby a fine aerosol of an encapsulant is generated to encapsulate contaminants within a contaminated environment. The aerosol is generated by one or more ultrasonic transducers located below the surface of a reservoir containing a liquid. The output of the transducers is focused to either a point and/or directed toward an area near the surface of the liquid to cause a surface disturbance, which results in the formation of an aerosol from the liquid. The transducers used in these apparatuses are made from lead-zirconate-titanate-four (PZT-4) or other piezoelectric materials. This material is coated with a conductive coating (electrode material) that enables an electrical signal to energize the transducer and causes it to emit high frequency pressure (energy).
While operating these prior art apparatuses and similar apparatuses, it has been found that certain liquids, especially acidic solutions, chemically react with the electrode materials of the transducers that generate the aerosol. The result is a noticeable deterioration of both the transducers and their performance. For example, acidic solutions of hydrogen peroxide and peroxyacetic acid have caused noticeable deterioration of the transducers within minutes of operation.
An attempt was made to prevent transducer degradation by coating the face of the transducers with a thin coating of different materials. None of these efforts have been successful. For example, U.S. Pat. No. 4,109,863, which is incorporated herein by reference in its entirety, including any references cited therein, discloses similar findings. The protective coating on the transducer deteriorated to a point where the transducer failed to be energized. It was initially believed that this deterioration was caused by transducer induced cavitation within the tank; however, the aforementioned coatings were also shown to fail in simple immersion tests, conducted over time in an acidic solution, with unpowered transducers. For example, laboratory work indicated that PZT material coated with an electroless nickel plating, or a glaze, were both found to be incompatible with a 4% solution of hydrogen peroxide and peroxyacetic acid, after being exposed to the solution for two weeks at 160° F.
In addition, it was found that various materials used to construct the transducer housing and assembly experienced deterioration after being subjected to a simulated long-term exposure to an acid solution of hydrogen peroxide and peroxyacetic acid. This was observed with an accelerated aging test. This test consisted of placing components constructed of various material types in vessels containing the hydrogen peroxide and peroxyacetic acid solution and subjecting them to increased temperature over a course of time. Without being limited to the theory, this test is based on the theory recognized in the art that at higher temperatures chemical or physical reactions will proceed faster due to the increased probability that two molecules will collide and chemically react.
Without being limited to a particular mechanism, method, or chemical, it is believed that chemically reactive liquids are necessary in sterilization processes to contact contaminants including but not limited to toxins, bacteria, virus, fungus, and spores (both fungal and bacterial), prions or protein structures, within a target area(s) either killing the bacteria, fungus, or spores, neutralizing or destroying toxins, or rendering a protein structure incapable of replication or otherwise interfering with the target's cellular physiology. These chemically reactive liquids may be provided as an aerosol. For example, U.S. Pat. No. 4,512,951, which is incorporated herein by reference in its entirety, including any references cited therein, teaches using hydrogen peroxide to sterilize medical devices by condensing hydrogen peroxide-water vapors to deposit a film of liquid on the devices. The liquid film is then evaporated.
While the prior art attempted to coat the transducer with a protective substance, there were problems with these coatings. U.S. Pat. Nos. 3,729,138; 4,109,863; and 4,976,259, each of which is incorporated herein by reference in its entirety, including any references cited therein, teach that the optimum thickness of a glass barrier, which may be used as a protective plate and/or cover, on a transducer should be any multiple of one-half (½) the wavelength of the transmitted pressure (energy). The thicknesses of protective barriers have been calculated using wave transmission theories and their respective mathematical formulas known to those skilled in the art. It is estimated that twenty percent (20%) of the energy emitted from the transducers is being transmitted into the liquid beyond the protective barrier. The prior art does not include techniques for further increasing the energy emitted from the transducer with a protective plate and/or cover.
U.S. Pat. Nos. 3,433,461; 3,729,138; 4,109,863; and 4,976,259, each of which is incorporated herein by reference in its entirety, including any references cited therein, teach that an effective thickness of a protective barrier material “interfaced with” a transducer can be approximately any multiple of one-half (½) the wavelength of the transmitted pressure (energy) from the transducer. Prior art has taught that barriers having a thickness equal to or about one-half (½) wavelength constructed from non-conductive and/or insulating type materials like glass, could be effectively coupled with an ultrasonic transducer for generating aerosol, as long as they included a special design consideration for cooling the transducer, or the transducer was separated from the glass barrier with a layer of liquid. U.S. Pat. No. 3,433,461 teaches utilizing a 1.5 inch diameter transducer bonded to a metal barrier that is a one-half wavelength thick. A problem associated with using metal barriers is corrosion, which was acknowledged in U.S. Pat. No. 3,729,138. In addition, U.S. Pat. No. 3,433,461 discloses that heat has a detrimental effect associated with the operation of a transducer and that a metal barrier interfaced with a transducer permitted the use of much higher driving powers than in prior art devices, since it provided more heat dissipation. Further, the driving power supplied to the transducers is limited by the heat dissipation in the device, which is a function, in each case, of the total area of the generator.
According to U.S. Pat. No. 4,976,259, an attempt was made to bond a glass barrier to a piezoelectric crystal with an adhesive, but such an attempt did not improve on the prior art and resulted in a major loss of acoustic coupling of the ultrasonic energy into the glass cover as the adhesive bond deteriorated. The deterioration was due to high localized temperatures caused by reflected energy resulting from mismatched acoustical impedances.
The prior art does not currently include commercially effective techniques for constructing and operating a high frequency and high power aerosol producing transducer assembly consisting of one or more transducers bonded or adhered to a protective barrier constructed from non-metallic and/or insulative type materials, such as glass, with a thickness that is not one-half (½) of a wavelength. Furthermore, the prior art does not currently include high frequency and high power aerosol producing glass barrier and transducer assemblies that are capable of operating without additional liquid layers or liquid cooling means incorporated into the transducer assembly design.
Therefore, the need for a protective barrier for the aerosol producing transducer that is highly resistant to degradation caused by chemically reactive solutions exists. The protective barrier should withstand the heat generated by a transducer and should function effectively with the transducer to produce a fine aerosol at high output levels (which requires high energy emitted by the transducer). This heat is due to the high frequency and energy that is needed to achieve a high output of aerosolized liquid per hour with the aerosol droplets being less than about 10 microns in size. In general, within the effective frequency band, the higher the power at the effective aerosol producing frequencies, the larger the quantity of aerosol produced; and the higher the effective frequency the smaller the droplet size in the aerosol.
The complete and assured sanitization, disinfection, high-level disinfection, or sterilization of devices, tools, machinery, or other objects or surfaces, within enclosed or unenclosed targeted areas or surfaces, related to industries including, but not limited to, health care, food production, medical device or products, clean rooms, and pharmaceutical, has always been a challenge in terms of overall effectiveness, processing time, cost, and engineering tradeoffs. In addition, the applied agents must have limited toxicity, be reasonably safe, as well as non-harmful to the materials or substances to which they are applied.
The prior art has extensively taught that relatively quick disinfection and sterilization of surfaces can be achieved by exposing them to an aerosol of a disinfectant/sterilizing agent created by ultrasonic nebulization. The apparatus described in U.S. Pat. No. 4,366,125 (Kodera et al., 1980), which is incorporated herein by reference in its entirety, including any references cited therein, generates a hydrogen peroxide mist by an ultrasonic waves vibrator. The aqueous hydrogen peroxide is heated as it travels from a tank into a basin (col. 4, line 6-8) where it is turned into a fog or mist as the surface of the germicidal liquid in the basin is acted upon by ultrasonic waves. The fog or mist will adhere to the surface of materials being sterilized or disinfected. The surface is then irradiated with ultraviolet-ray lamps.
G.B. Patent No. 1,128,245, (Rosdahl et al., 1968) which is incorporated herein by reference in its entirety, including any references cited therein, describes a device for disinfecting apparatuses and instruments, including medical instruments. This apparatus also generates a mist of disinfectant, including hydrogen peroxide, by means of an ultrasonic aerosol generator. According to Rosdahl et al., this patent was “primarily adapted for the disinfection of small medical instruments such as scalpels, tongs, syringes, or the like, positioned on a grid in a container” (pg. 3 col. 23-30). However, another separate intended use for a second described apparatus was to disinfect the interior surfaces of objects such as hollow tubing used for “breathing apparatuses” and “heart lung machines” (pg. 1 line 30-36 and pg 2 line 95-101). Rosdahl et al. also taught the use of the germicidal fogging technology to disinfect rooms, apartments and the like (pg. 2 col. 28-30). The pressurized air in Rosdahl et al. is supplied by way of a fan etc. or carrier gas, (pg. 2 line 48-49) and is used to move the generated aerosol as well as to dry objects placed within the enclosed area of the described apparatus. Rosdahl et al. also incorporated “a heating element in the flow path of the carrier gas, to increase drying efficiency” (pg. 3 line 123-127).
Ultrasonic nebulizers have a unique advantage in that they can create aerosol droplets less than 10 microns in size depending on the power and frequency used in their operation. The small size of the droplets enables them to penetrate small cracks and crevices and to behave like a gas due to Brownian movement and diffusion. In addition, the dense cloud of small droplets is able to form a very thin coating or film over surfaces. The thin coating or film of disinfectant or sterilization agent is able to dry much faster than coatings created by aerosols consisting of larger diameter droplets. It is also theorized that even partial contact of the aerosol droplets with the targeted contaminate(s), can contribute to the overall efficacy of the process. U.S. Pat. No. 4,366,125, (Kodera et al., 1980) taught that heated H2O2 was more efficacious than H2O2 used at room temperature (col. 1, line 19-25). In other words, (Kodera et al., 1980) taught that the efficacious nature of a liquid agent can be increased as it is heated to temperatures higher than ambient temperature. This is desired, without limitation, in the present invention. The text entitled, “Aerosol Technology” by William C. Hinds (1982), which is incorporated herein by reference in its entirety, including any references cited therein, also taught that the size of the aerosol particles produced by ultrasonic means is not only affected by the frequency of the transducer operation, but also by the surface tension and density of the liquid as shown by the following mathematical expression (page 382):CMD=((y)/(pL)(f^2))^1/3  Equation 1                where: CMD=particle size produced; y=surface tension; pL=liquid density; and f=frequencyIt is commonly known that heating a liquid to point less than its boiling point will reduce its surface tension. Therefore, according to Equation 1 above, a direct relationship was established by William C. Hinds (1982) where one skilled in the art can ascertain that the higher the temperature of the liquid, the lower the liquid's surface tension, which will result in smaller sized aerosol particles. This principal is incorporated without limitation, in the present invention. William C. Hinds (1982) also taught in the same text that smaller diameter particles demonstrate characteristics such as but not limited to, a lower settling velocity, a higher diffusion coefficient, and a higher Brownian displacement (movement), which is desired, without limitation, in the present invention. William C. Hinds (1982) further taught that ultrasonic aerosol generating transducers can heat the surrounding liquid (page 382). This is also desired in the present invention.        
Despite the plethora of advancements shown in the current art, limitations exist in many areas that reduce the effectiveness or viability of the ultrasonic aerosol generator technology in actual commercial applications. The methods and apparatuses of the present invention address the need for an ultrasonic aerosol generator that is, without limitation: (a) designed so that the apparatus can be quickly and easily set up and operated in a reproducible manner on uneven or angled surfaces(s), (b) designed so that the transducers can quickly heat the liquid and liquid surface above and/or around them, (c) designed to prevent or limit dust and debris contamination inside the pressurized air channels or pipes of the apparatus or in the tank in which one or more transducer(s) are located, (d) designed so that if a valve of a liquid storage, holding tank, or reservoir, breaks the tank(s) or reservoir(s) in which the transducer(s) is located is not flooded, (e) designed so that excess, leaked, or spilled liquid can be transferred to a separate containment tank or basin from sources such as but not limited to the fill pipe(s), blower housing(s), internal catch pan(s), transducer tank(s) or basin(s), (f) designed so that the liquid in the tank in which the transducers are located does not drop below the minimum or exceed the maximum operating temperature for that liquid or particular process, coupled with one or more sensor(s) that can determine when an effective or sufficient amount of aerosol has been applied or administered to the targeted area and/or surfaces, (g) designed so that a partially empty apparatus can be easily and effectively refilled, (h) designed to prevent expired liquid that has been added or is otherwise available to the apparatus from being administered by or deployed from the apparatus, (i) designed so that the stream of aerosol deployed from the apparatus can be simultaneously delivered to one or more separate areas.
It is obvious to those skilled in the art that an apparatus can automatically shut down if an insufficient amount of inventory or product is available with which to complete its defined operational cycle. This activity is also mentioned in French Patent No. FR2860721 (Schwal et al.), which is incorporated herein by reference in its entirety, including any references cited therein. This patent claims the use, by any aerosol generator, of single-use liquid refill/fill cartridges that are associated with specific identifiers, and a reader integrated into the aerosol generator apparatus that can read the said identifiers, all of which is dependently combined with a system of defined steps to establish a set process whereby the apparatus will not generate aerosol if there are any non-conformances related to the entire process, and each cycle of use is terminated with a recording of various information pertaining to the process as a whole. However, according to patent No. FR2860721, the apparatus only notifies the operator if an insufficient liquid quantity is available (pg. 6 line 15-25 and pg. 10 line 10-25) and when it is necessary to replace a filler cartridge (pg. 10 line 15-25).
Patent No. FR2860721, does not teach or describe an aerosol generator apparatus that can communicate, by any means, to the apparatus operator the quantity of liquid or at least the exact minimum quantity of liquid, expressed in units of measurement, that is necessary to add or make available to the apparatus so that it may successfully complete its desired or chosen operational time or run cycle. The methods and apparatuses of the present invention address the need to provide this information.
French Patent No. FR2860721 also fails to address the issue of preventing the apparatus from using expired or outdated liquid that is available to the apparatus from, without limitation, one or more tanks or reservoirs inside or attached to the apparatus that have been fed, supplied, or filled by a refill/fill cartridge or other means. This is critical since some liquid agents have a defined period of time of efficacious use once they have undergone, without limitation, dilution from a concentrate or exposure to air. The methods and apparatuses of the present invention address the need to prevent the use or deployment of a liquid agent that is available to the apparatus, but has expired, is unusable, or undesired.
The need for an ultrasonic aerosol generator that can be positioned and operated from within the area in which the aerosol is being dispersed so as to, without limitation, eliminate or reduce the effects of increased air pressure within the targeted area and operate without damage to its internal and external structures and components is also addressed in the present invention and includes, without limitation, methods and apparatuses such as: (a) means for cooling the various motors, electronics, and other components; (b) properly housing various motors, electronics, and other components to prevent their exposure to the environment surrounding the apparatus; (c) the remote control of and remote communication with the apparatus; (d) preventing any parts of the apparatus that are exposed to the aerosol from becoming higher in temperature than the temperature of the atmosphere surrounding the apparatus.
There is also a continued need in the market place to increase efficacy and effectiveness from the aerosol and the process of its administration, as well as a system that offers shortened cycle times. The present invention addresses these issues. One such means in the present invention is the utilization of thermal forces and their resultant effects, by cooling or decreasing the temperature of the objects, the atmosphere in which they reside, or the targeted area for the administration of an aerosol as well any surfaces in that area, before the administration of the aerosol to the targeted area or surfaces. Prior art has taught the step of cooling an enclosed area and its surfaces before the administration of a hydrogen peroxide disinfectant, however the hydrogen peroxide was first vaporized into a gaseous state before its administration, and the cooling step was intended to condense the vaporized hydrogen peroxide gas out of the atmosphere in which it was administered and onto the intended surfaces, as taught in U.S. Pat. No. 4,512,951 (Koubek et al., 1983), which is incorporated herein by reference in its entirety, including any references cited therein. More specifically, Koubek et al., teaches a method of sterilization where a liquid of aqueous hydrogen peroxide is vaporized, and the uniformly vaporized mixed hydrogen peroxide-water vapors are delivered into an evacuated sterilizer chamber. The articles to be sterilized are cooled if necessary prior to the introduction of the vapor (or are cooled by the evacuation of air from the sterilizing zone) to a temperature below the dew point of the entering vapors and the condensing vapor deposits a film of liquid on all such cool surfaces (col 2, line 40-51). Koubek et al., also mentions in claim 2 that the result of vaporization was a mixed “gaseous vapor” consisting of hydrogen peroxide and water vapor free of solid contaminants.
U.S. Pat. No. 4,952,370 (Cummings et al., 1988), which is incorporated herein by reference in its entirety, including any references cited therein, teaches a similar method of sterilization where a liquid of aqueous hydrogen peroxide is also vaporized into a gaseous state before its administration into an evacuated sterilizer chamber. However, Cummings et al., teaches improvements to the art where the hydrogen peroxide-water vapor is applied under vacuum to surfaces that are below 10 degree centigrade, or surfaces in an environment that are both below 10 degree centigrade and above 10 degree centigrade. The cold surfaces mentioned in Cummings et al., were not cooled to accentuate or enhance the process, but were surfaces of components that were inherently cold for their own operational purposes. This is mentioned in sections such as (col 2, line 4-9), (col 2, line 29-33), and (col 4, line 67 to col 5, line 2).
U.S. Patent Application No. 2005/0042130 A1 (Lin et al., 2003), which is incorporated herein by reference in its entirety, including any references cited therein, claims the use of an applied vacuum to move an ultrasonically derived aerosol, consisting of a sterilant, throughout the area of an enclosed chamber. The use of various vacuum pressures below atmospheric pressure was also mentioned as well as the possibility that vacuum pressures lower than 5 torr lower than atmospheric pressure would likely “enhance the results”, and that using a vacuum pressure low enough to vaporize the sterilant generally enhances sterilization (pg. 2, paragraph 28). However, Lin et al, was silent with respect to how the lower vacuum pressures would “enhance the results” other than any enhancement that vaporization of the aerosol might bring. Lin et al, was also silent with respect to the amount of time that is needed to elapse between lowering the pressure within the enclosed chamber and the application of an aerosol, in order to obtain the needed or desired level of efficacy. (Lin et al., 2003) was silent with respect to cooling any surfaces within the sterilization chamber or applying the aerosol to any cooled surfaces.
It is important to note that Lin et al, did not mention any process or method to heat the liquid of the aerosol or cool the surfaces in the sterilization chamber before or during the delivery of the aerosol, or any means to incur condensation if the liquid was vaporized. In fact, the 5 torr negative pressure that was used by Lin et al. to generate their findings was reported to be sufficient enough to disperse the mist within the sterilization chamber (pg. 2, paragraph 28), but was never mentioned to have cooled the surfaces within the sterilization chamber or to have that intended effect.
In addition, it is important to note that the cooling of a targeted environment(s) and/or the surfaces contained therein addressed by the present invention is intended, without limitation, for a completely different application and purpose. The present invention utilizes the principals of aerosol behavior to increase the performance of the process of the present invention, and not the condensation of a gas as taught in the prior art. This is further addressed in the present invention.
By comparison, the current invention utilizes, without limitation, the cooling of the targeted environment(s) and its surfaces to enhance the performance and efficacy of the aerosol administration process and not to condense a gas as taught by the prior art. The methods and apparatuses of the present invention also address the need to apply an aerosol to surfaces that are without limitation, difficult, impossible, time consuming, or not cost effective to enclose.